1. Technical Field
The present invention relates to a control apparatus for a vehicle headlight and a control method therefor, and in particular relates to a control apparatus for a vehicle headlight, which performs transition control over a light distribution pattern having a plurality of modes, and a control method therefor.
2. Background Art
Vehicle headlights in general are able to switch a beam from high to low, or vice versa. A low beam casts short-range light ahead of the vehicle, with a predetermined illuminance so that no glare is given to vehicles traveling ahead, including oncoming vehicles or preceding vehicles. Thus, a low beam is mainly used in travel in a residential area. On the other hand, a high beam illuminates a broad area and casts long-range light ahead of the vehicle, with a comparatively high illuminance. Thus, a high beam is mainly used on a road where only a few vehicles travel ahead. Compared to a low beam, a high beam promises better visibility to the driver but suffers from a problem of causing glare to the drivers of other vehicles. Accordingly, in many cases, a low beam is particularly used in night-time travel in an urban area. On the other hand, there is an implementation in which a beam mode is switched to a high-beam light distribution mode, in response to a need of improving a driver's visibility of a road in a low-beam state. Specifically, after analysis of image information obtained from an in-vehicle camera for acquisition of the surrounding illuminance or brightness, if the vehicle speed is less than a predetermined speed, with no vehicle being detected as traveling ahead, with a resultant determination that the area is a residential area, the beam mode is switched to the high-beam light distribution mode, as a residential mode, that does not cause glare to pedestrians.
Patent Literature 1 describes that a vehicle speed of not more than a predetermined speed is set as an antiglare speed range for pedestrians. According to the description, when a vehicle speed is in the antiglare speed range for pedestrians, the vehicle is determined to be traveling in a residential area, and the illuminance is lowered such as with a light distribution pattern for high beam.
Patent Literature 1 JP-A-2011-005992